1. Technical Field
Embodiments generally relate to techniques for power management in a computer platform. More particularly, certain embodiments provide a method for saving or retrieving state of a processor in support of transitioning a computer platform between processor power states.
2. Background Art
Improvements in integrated circuit (IC) fabrication and in other aspects of computer device manufacturing have allowed for smaller and/or more densely integrated platform architectures. The circuitry in such platforms is generally trending toward increasing sensitivities to inefficiencies in power use and/or increasing sensitivities to inefficient use of die space. Consequently, incremental improvements in power efficiency, die size and/or die utilization provide increasingly large performance gains in such platforms. This is particularly so in the case of small form factor platforms such as those of handheld devices—e.g. smart phones, tablets and the like.
Existing computer platforms variously include one or more features for managing the distribution of power to, or use of power by, processors of such platforms. For example, such features may variously implement a processor idle state, for example, in response to a user initiated platform suspend, or hibernate, request. To support a processor idle power state such as the C6 power state, a platform must assure that state information of the processor is not lost during a period of time when the processor is in that processor idle power state. In existing technologies, processors variously include dedicated hardware for either offloading processor state to differently-powered areas on-chip or for continuously maintaining processor state in a specialized power domain which is separate from another, general power domain of the processor.
Reliance on such techniques for implementing a processor idle power state has imposed a requirement that various implementing circuitry—e.g. one or more of registers, power distribution traces, control logic, etc.—be included on the processor's IC chip. Such requirements have up to now imposed certain its on efforts to reduce, and/or to improve the utilization of, the die space of processors.